NEET Nuclei PYQs & Practice Questions

10 free NEET Physics questions on Nuclei, starting with previous year questions (2016–2026). Tap “Show answer” to check each one. No login needed.

Topics: Radioactivity · Nuclear Size and Density · Binding Energy · Radioactive Decay · Nuclear Reactions – Fission and Fusion · Mass-Energy Equivalence and Q-value · Radioactive Decay Law · Nuclear Force · Alpha, Beta, and Gamma Decay · Binding Energy and Nuclear Stability · Radioactivity – Activity and Decay · Alpha, Beta and Gamma Decay

1. Q1NEET 2026Q-value of a Nuclear Reaction

   Consider the following nuclear reaction: ²³⁸U → ²³⁴Th + ⁴He. Take masses of ²³⁸U, ²³⁴Th and ⁴He as 238.050 u, 234.043 u and 4.003 u, respectively. The Q value for the reaction, in keV, is: [Given: 1 u = 931.5 MeV c⁻²]

   • A. 3730
   • B. 3736
   • C. 3740
   • D. 3726
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   Answer: C — 3740

   Mass defect Δm = 238.050 - (234.043 + 4.003) = 238.050 - 238.046 = 0.004 u. Q = Δm × 931.5 MeV = 0.004 × 931.5 = 3.726 MeV = 3726 keV.

2. Q2NEET 2026Mass number and mass defect statements

   Four statements are given (A is mass number): A. Volume of a nucleus is proportional to A^(1/3). B. Volume of a nucleus is proportional to A. C. Difference in mass of an atom and its nucleus is called the mass defect. D. Difference in mass of a nucleus and its constituents is called the mass defect. Choose the correct answer:

   • A. A and D are true, but B and C are false
   • B. B and D are true, but A and C are false
   • C. B and C are true, but A and D are false
   • D. A and C are true, but B and D are false
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   Answer: A — A and D are true, but B and C are false

   Nuclear volume ∝ A (B true, A false); mass defect = difference between mass of nucleus and sum of constituent masses (D true, C false). So B and D are true.

3. Q3NEET 2026Nuclear density and mass number

   An unknown nucleus has a nuclear density of 2.29×10¹⁷ kg/m³ and mass of 19.926×10⁻²⁷ kg. Its mass number A is approximately: (R0=1.2×10⁻¹⁵ m, 4π=12.56)

   • A. 16
   • B. 20
   • C. 12
   • D. 19
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   Answer: B — 20

   Using density=mass/[(4/3)πR³] with R=R0A^(1/3), solving gives A≈12.

4. Q4NEET 2024Nuclear Decay Series - Mass Number and Atomic Number

   ²⁹⁰₈₂X →(α) Y →(e⁺) Z →(β⁻) P →(e⁻) Q In the nuclear emission stated above, the mass number and atomic number of the product Q respectively, are:

   • A. 288, 82
   • B. 286, 81
   • C. 280, 81
   • D. 286, 80
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   Answer: A — 288, 82

   X(290,82) → α decay → Y(286,80) → e⁺ (positron) emission decreases Z by 1 → Z(286,79) → β⁻ decay increases Z by 1 → P(286,80) → e⁻ emission (β⁻-like) increases Z by 1 → Q(286,81). So Q has mass number 286 and atomic number 81.

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5. Q5NEET 2023Radioactive Decay - Half Life Calculation

   The half life of a radioactive substance is 20 minute. In how much time, the activity of substance drops to (1/16)th of its initial value?

   • A. 40 minutes
   • B. 60 minutes
   • C. 80 minutes
   • D. 20 minutes
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   Answer: B — 60 minutes

   Using A/A0 = 1/2^n, we get 1/16 = 1/2^n, so n = 4. Time t = n × T(half) = 4 × 20 = 80 minutes.

6. Q6NEET 2022Beta-Plus Decay Nuclear Reaction

   In the given nuclear reaction, the element X is: ²²₁₁Na → X + e⁺ + ν

   • A. ²³₁₀Ne
   • B. ²²₁₀Ne
   • C. ²²₁₂Mg
   • D. ²³₁₁Na
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   Answer: A — ²³₁₀Ne

   ²²₁₁Na → ᴬ_Z X + ₁e⁰ + ν. Charge conservation: 11 = Z+1 ⟹ Z=10. Mass conservation: A=22. So X is ²²₁₀Ne.

7. Q7NEET 2022Nuclear Decay - Positron Emission

   In the given nuclear reaction, the element X is: Na-22 (atomic number 11) -> X + e+ + neutrino

   • A. Na-23 (atomic number 11)
   • B. Ne-23 (atomic number 10)
   • C. Ne-22 (atomic number 10)
   • D. Mg-22 (atomic number 12)
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   Answer: B — Ne-23 (atomic number 10)

   In positron (e+) emission, a proton converts to a neutron, so the atomic number decreases by 1 while mass number stays the same. Na-22 (Z=11) becomes Ne-22 (Z=10).

8. Q8NEET 2022Nuclear Radius vs Mass Number

   A nucleus of mass number 189 splits into two nuclei having mass number 125 and 64. The ratio of radius of two daughter nuclei respectively is:

   • A. 1:1
   • B. 4:5
   • C. 5:4
   • D. 25:16
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   Answer: B — 4:5

   Nuclear radius R is proportional to A^(1/3). Ratio = 125^(1/3) : 64^(1/3) = 5:4.

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9. Q9NEET 2022Nuclear Reactions

   In the given nuclear reaction, the element X is: ²²₁₁Na → X + e⁺ + v

   • A. ²³₁₁Na
   • B. ²³₁₀Ne
   • C. ²²₁₀Ne
   • D. ²²₁₂Mg
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   Answer: B — ²³₁₀Ne

   In positron (β⁺) decay, atomic number decreases by 1, mass number unchanged: ²²₁₁Na → ²²₁₀Ne + e⁺ + v.

10. Q10NEET 2021Binding Energy Gain in Nuclear Fission

    A nucleus with mass number 240 breaks into two fragments each of mass number 120, the binding energy per nucleon of unfragmented nuclei is 7.6MeV while that of fragments is 8.5MeV. The total gain in the Binding Energy in the process is:

    • A. 216MeV
    • B. 0.9MeV
    • C. 9.4MeV
    • D. 804MeV
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    Answer: —

    Gain in binding energy Q = Binding energy of products − Binding energy of reactants = (120×8.5×2) − (240×7.6) = 2040 − 1824 = 216 MeV.